Cereals of the world Origin, Classification, Types Quality Wheat derived from separate ancestors, and which differ in chromosome numbers. One classification of Origin the races, with the probable wild types, chromo- The cultivation of wheat(Triticum spp. reaches some numbers(2n)and the cultivated forms is far back into history, and the crop was predomi- shown in Table 4.I nant in antiquity as a source of human food. It ie. the lemmaand palea form a husk which remains was cultivated particularly in Persia (Iran), Egypt, around the kernel after threshing. Emmer was used Greece and Europe. Numerous examples of ancient for human food in prehistoric times(cf. p. 95) wheat have been unearthed in archaeological investigations; the grains are always carbonized, there is archaeological evidence that it was grown although in some cases the anatomical structure about 5000 B.C. in Iraq. The principal wheats of is well preserved commerce are varieties of the species Taestivum T durum(cf p. 86)and T compactum(cf p 85) Races and species of wheat Common or Bread Wheat, T. aestivum(hexa ploid 2n= 42)is an allopolyploid; three genomes, The many thousands of known species and each corresponding to a normal diploid set of varieties of the genus Triticum(wheat) can be chromosomes, are distinguishable and are known grouped into three distinct races which have been to have had separate origins in the past Wild and Cultivated Wheat Types Cultivated forms Race Wild type 2n Species Common name Small spelt T Einkorn dicoccoides T. dicoccum Emmer Macaroni wheat urum T et. Cone A
4 Cereals of the World: 0 rig i n, CI assif icatio n, Types, Quality Wheat derived from separate ancestors, and which differ in chromosome numbers. One classification of the races, with the probable wild types, chromosome numbers (2n) and the cultivated forms is shown in Table 4. 1. Einkorn, emmer and spelt are husked wheats, i.e. the lemma and palea form a husk which remains around the kernel after threshing. Emmer was used for human food in prehistoric times (cf. p. 95); there is archaeological evidence that it was grown about 5000 B.C. in Iraq. The principal wheats of commerce are varieties of the species T. aestivum, T. durum (cf. p. 86) and T. compactum (cf. p. 85). Common or Bread Wheat, T. aestivum (hexaploid 2n = 42) is an allopolyploid; three genomes, each corresponding to a normal diploid set of chromosomes, are distinguishable and are known to have had separate origins in the past. Origin The cultivation of wheat (Triticum spp.) reaches far back into history, and the crop was predominant in antiquity as a source of human food. It was cultivated particularly in Persia (Iran), Egypt, Greece and Europe. Numerous examples of ancient wheat have been unearthed in archaeological investigations; the grains are always carbonized, although in some cases the anatomical structure is well preserved. Races and species of wheat The many thousands of known species and varieties of the genus Triticum (wheat) can be grouped into three distinct races which have been TABLE 4.1 Wild and Cultivated Wheat Types ~ Cultivated forms Race Wild type 2n Species name Common name Small spelt T. aegilopoides 14 T. mmococcum Einkorn Emmer T. dicoccoides 28 T. dicoccum Emmer T. durum Macaroni wheat T. polonicum Polish T. turgidum Rivet, Cone probably 42 T. aestivum Bread wheat T. mmococcum T. spelta Dinkel, Spelt X T. speltoides T. compactum Club x Ae. squarrosa T. sphaerococcum Indian Dwarf (durum) 1 Large spelt Dinkel 7a
CEREALS OF THE WORLD The hexaploid wheats are believed to have vitreous and mealy wheats arisen by hybridization of the diploid species T. tauschii (Aegilops squarrosa) with the tetraploid The endosperm texture may be vitreo flinty, glassy, horny) or mealy(starchy speltoides), two diploid species, with doubling of Samples may be entirely vitreous or he chromosomes. Evidence points to the spelta and mealy grains, with one type predominating group as being the oldest of the hexaploids, with Individual grains are generally completely vitreous the aestivum group having arisen from the spelta group by mutation of a single gene, and the or completely mealy but grains which are partly compactum and sphaerococcum groups having arisen vitreous and partly mealy (piebald'or 'metadine' from aestivum similarly by the mutation of single are frequently encountered. The specific gravity genes. The evidence is presented by Quisenberry of vitreous grains is generally higher than that of and Reitz (1967) mealy grains: 1.422 for vitreous, 1. 405 for mealy Cultivated varieties, which are of widely differ- (Bailey, 1916) The vitreous or mealy character is hereditary ing pedigree and are grown under varied condi- but is also affected by environment. Thus, T. tions of soil and climate show wide variations in characteristics aegilopoides, T. dicoccoides, T. monococcum and T The climatic features in countries where spring T. turgidum and many varieties of T. compactum heat is grown- maximum rainfall in spring and T aestivum are mealy(Percival, 1921).How- nd early summer, and maximum temperature in the mid-and late-summer_favour production ever, the vitreous/mealy character may be modi- of rapidly maturing grain with endosperm of fied by cultural conditions. Mealiness is favoured vitreous texture and high protein content, tradi- by heavy rainfall, light sandy soils, and crowded tionally suitable for breadmaking. Winter wheat, planting and is more dependent on these condi- grown in a climate of relatively even temperature tions than on the type of grain grown.Vitreousness and rainfall, matures more slowly, producing a can be induced by nitrogenous manuring or crop of higher yield and lower nitrogen content, commercial fertilizing and is positively correlated with better suited for biscuit and cake-making tha high protein content; mealiness is positively for bread, although in the U. K, where winter correlated with high grain-yielding capacity wheat comprises about 96% of the total (cf Vitreous kernels are translucent and appear bright against a strong light, whereas mealy p. 87), winter wheat is used for breadmaking. kernels are opaque and appear dark t under similar he yield of durum wheat(cf. p. 86), which is grown in drier areas, is lower than that of bread cIrcumstances. The opacity of mealy kernels is an optical effect due to the presence of minute The high-yielding Indian wheats, devele vacuous or air-filled fissures between and perhaps for u in the Green Revolution(cf. p 6), make within the endosperm cells. The fissures form chapatties(cf p. 270)of indifferent quality Brown internal reflecting surfaces, preventing light trans- mission, and giving the endosperm a white ance. Such fissures are absent from vitreous endosperm Wheat types The development of mealiness seems to be In a general way wheats are classified accord- connected with maturation, since immature grains ng to(1)the texture of the endosperm, because of all wheat types are vitreous, and vitreous grains this characteristic of the grain is related to the are found on plants that grow and ripen quickly way the grain breaks down in milling, and( 2) spring wheats, and those growing in dry conti he protein content, because the properties of the nental climates. Mealy grains are characteristic flour and its suitability for various purposes are of varieties that grow slowly and ha related to this characteristic maturation period
CEREALS OF THE WORLD 79 The hexaploid wheats are believed to have arisen by hybridization of the diploid species T. tauschii (Aegilops squawosa) with the tetraploid speltoides), two diploid species, with doubling of the chromosomes. Evidence points to the spelta the aestivum group having arisen from the spelta group by mutation of a single gene, and the compacturn and sphaerococcum groups having arisen Vitreous and mealy wheats The endospem texture may be viveous (steely, flinty, glassy, horny) or mealy (starchy, chalky). mealy, or may consist of a mixture of vitreous and mealy grains, with one type predominating. or completely mealy, but grains which are partly vitreous and partly mealy ('piebald' or 'metadink') are frequently encountered. The specific gravity hybrid Of T. monococcum and T. spe1toides (Ae. Samples may be entirely vitreous or entirely group as being the Oldest Of the hexap1oids, with Individual gr,&s are generally completely vitreous from aestivum simi1ar1y by the mutation Of sing1e of vitreous grains is generally higher than that of genes. The evidence is presented by Quisenberry mealy grains: 1.422 for VitreOUS, 1.405 for mealy and Reitz (1967). (Bailey, 1916). Cultivated varieties, which are of widely differing pedigree and are grown under varied conditions of soil and climate, show wide variations in characteristics. The climatic features in countries where spring wheat is grown - maximum rainfall in spring and early summer, and maximum temperature in the mid- and late-summer - favour production of rapidly maturing grain with endosperm of vitreous texture and high protein content, traditionally suitable for breadmaking. Winter wheat, grown in a climate of relatively even temperature crop of higher yield and lower nitrogen content, better suited for biscuit and cake-making than The vitreous or mealy character is hereditaw, but is also affected by environment. Thus, T. aegilopoides, T. dicoccoides, T. monococcum and T. durum are species with vitreous kernels, whereas T. turgidurn and many varieties of T. compactum and T. aestivum are mealy (Percival, 1921). However, the vitreous/mealy character may be modified by cultural conditions. Mealiness is favoured by heavy rainfall, light sandy soils, and crowded planting, and is more dependent on these conditions than on the type of grain grown. Vitreousness can be induced by nitrogenous manuring or with high protein content; mealiness is positively correlated with high grain-yielding capacity. and rainfa11, matures more slOwlY, producing a commercial fertilizing and is positively correlated for bread, a1though in the U.K., where winter wheat comprises about 96y0 Of the tota1 (cf. PP' 87), winter wheat is used for breadmaking' The yield Of durum wheat (cf' P' 86), which is Vitreous kernels are translucent and appear bright against a strong light, whereas mealy kernels are opaque and appear dark under similar circumStanceS. The opacity of mealy kernels is an optical effect due to the presence of minute vacuous or air-filled fissures between and perhaps internal reflecting surfaces, preventing light transmission, and giving the endosperm a white appearance. Such fissures are absent from vitreous endosperm. The development of mealiness seems to be of all wheat types are vitreous, and vitreous grains are found on Plants that grow and ripen quickly: spring wheats, and those growing in dry continental climates. Mealy grains are characteristic of varieties that grow slowly and have a long maturation period. grown in drier areas, is lower than that of bread wheat. for use in the Green Revolution (cf. p. 6), make chapatties (cf. p. 270) of indifferent quality (Brown, 1972). The high-yielding Indian wheats, deve1oped within the endosperm cells. The fissures form Wheat types ing to (1) the texture of the endosperm, because this characteristic of the grain is related to the way the grain breaks down in milling, and (2) the protein content, because the properties of the flour and its suitability for various purposes are related to this characteristic. In a general way, wheats are classified accord- connected with maturation, since immature grains
TECHNOLOGY OF CEREALS Vitreous kernels sometimes acquire a mealy comprised five polypeptides, but of higher M, appearance after being conditioned in various 59-149k. It has also been found that one particular ways, e.g. by repeated damping and drying, or polypeptide of the surface SGP, with Mr 15 k, is by warm conditioning(cf p 122). The proportion strongly present in all soft wheats examined, but of vitreous kernels in a sample is a characteristic only weakly present in hard(t aestivum) wheats used in grading some types of U.S. wheat(cf p. and completely absent from the very hard durum (T. durum) wheats. Hardness/softness of wheat endosperm is known to be genetically controlled Hard and soft wheats (Berg, 1947) by a gene, Ha, which is located on the 5d chromosome, and it was subsequentl Wheat types may also be classified as hard or discovered that the gene controlling the formation soft, and as strong or weak(see below). Vitreous of the Mr 15 k protein is also situated on the 5D grains tend to be hard and strong, mealy grains chromosome, and is either identical with the Ha to be soft and weak, but the association is not gene, or is located quite close to it. The Mr 15 k invariable protein has been named"friabilin'and it appears Hardness'and'softness'are milling characte- to act as a'non-stick agent, since it is strongly stics, relating to the way the endosperm breaks present in soft -endosperm wheats that fragment down. In hard wheats, fragmentation of the easily and at random, but is only weakly present endosperm tends to occur along the lines of in, or entirely absent from, hard wheats that frag- the cell boundaries, whereas the endosperm of ment only with difficulty, and generally not along soft wheat fractures in a random way. This the interface between starch granule and surround phenomenon suggests a pattern of areas of mech- ing protein matrix (Schofield and greenwell anical strength and weakness in hard wheats, but 1987; Greenwell, 1987; Greenwell and Schofield fairly uniform mechanical weakness in soft wheat. 1989) One view is that ' hardness'is related to the degree hard wheats yield coarse, gritty flour, free of adhesion between starch granules and the flowing and easily sifted, consisting of regular surrounding protein, viz. that differences in endo- shaped particles, many of which are whole sperm texture must be related to differences in the endosperm cells, singly or in groups. Soft wheats nature of the interface between starch granules give very fine four consisting of irregular-shaped and the protein matrix in which they are embedded fragments of endosperm cells (including a propor- (Barlow et aL. 1973; Simmonds, 1974). The tion of quite small cellular fragments and free interface was shown to be rich in water-extractable starch granules), with some fattened particles, proteins, although no specific biochemical com- which become entangled and adhere together, sift ponent that might control the adhesion between with difficulty, and tend to clog the apertures of starch granules surface and protein matrix was sieves (cf. p. 144). The degree of mechanical dentified(Simmonds et al., 1973) damage to starch granules produced during mill- Well-washed prime starch separated from wheat ing is greater for hard wheats than for soft(cf endosperm contains some 0. 15-0.2% by weight of pp. 62 and 149 protein-starch granule protein(SGP)-and Hardness affects the ease of detachment of the the SGP comprises about 1% of the total protein endosperm from the bran. In hard wheats the of the grain. Part of the SGP is located on the endosperm cells come away more cleanly and tend surface of the granules, the remainder is an to remain intact, whereas in soft wheats the sub integral part of the granule structure. Character- aleurone endosperm cells tend to fragment, a ization of the SGP by polyacrylamide gel electro- portion coming away while the rest remains phoresis in the presence of sodium dodecyl sulphate attached to the bran has shown that the surface SGP comprized five The granularity of four gives a measure of the polypeptides of low relative molecular mass(M_) relative hardness of the wheat, the proportion of from 5 to 30 k, while the integral SGP also the flour passing through a fine flour silk(when
80 TECHNOLOGY OF CEREALS Vitreous kernels sometimes acquire a mealy comprised five polypeptides, but of higher M,: appearance after being conditioned in various 59-149 k. It has also been found that one particular ways, e.g. by repeated damping and drying, or polypeptide of the surface SGP, with M, 15 k, is by warm conditioning (cf. p. 122). The proportion strongly present in all soft wheats examined, but of vitreous kernels in a sample is a characteristic only weakly present in hard (T. aestzvurn) wheats, used in grading some types of U.S. wheat (cf. p. and completely absent from the very hard durum 85). (T. durum) wheats. Hardnesslsoftness of wheat endosperm is known to be genetically controlled (Berg, 1947) by a gene, Ha, which is located on the 5D chromosome, and it was subsequently Hard and soft wheats Wheat types may also be classified as hard or discovered that the gene controlling the formation soft, and as strong or weak (see below). Vitreous of the M, 15 k protein is also situated on the 5D grains tend to be hard and strong, mealy grains chromosome, and is either identical with the Ha to be soft and weak, but the association is not gene, or is located quite close to it. The M, 15 k invariable. protein has been named ‘friabilin’ and it appears ‘Hardness’ and ‘softness’ are milling characte- to act as a ‘non-stick’ agent, since it is strongly ristics, relating to the way the endosperm breaks present in soft-endosperm wheats that fragment down. In hard wheats, fragmentation of the easily and at random, but is only weakly present endosperm tends to occur along the lines of in, or entirely absent from, hard wheats that fragthe cell boundaries, whereas the endosperm of ment only with difficulty, and generally not along soft wheat fractures in a random way. This the interface between starch granule and surroundphenomenon suggests a pattern of areas of mech- ing protein matrix (Schofield and Greenwell, anical strength and weakness in hard wheats, but 1987; Greenwell, 1987; Greenwell and Schofield, fairly uniform mechanical weakness in soft wheat. 1989). One view is that ‘hardness’ is related to the degree Hard wheats yield coarse, gritty flour, freeof adhesion between starch granules and the flowing and easily sifted, consisting of regularsurrounding protein, viz. that differences in endo- shaped particles, many of which are whole sperm texture must be related to differences in the endosperm cells, singly or in groups. Soft wheats nature of the interface between starch granules give very fine flour consisting of irregular-shaped and the protein matrix in which they are embedded fragments of endosperm cells (including a propor- (Barlow et al., 1973; Simmonds, 1974). The tion of quite small cellular fragments and free interface was shown to be rich in water-extractable starch granules), with some flattened particles, proteins, although no specific biochemical com- which become entangled and adhere together, sift ponent that might control the adhesion between with difficulty, and tend to clog the apertures of starch granules surface and protein matrix was sieves (cf. p. 144). The degree of mechanical identified (Simmonds et al., 1973). damage to starch granules produced during millWell-washed prime starch separated from wheat ing is greater for hard wheats than for soft (cf. endosperm contains some 0.15-0.2% by weight of pp. 62 and 149). protein - ‘starch granule protein’ (SGP) - and Hardness affects the ease of detachment of the the SGP comprises about 1% of the total protein endosperm from the bran. In hard wheats the of the grain. Part of the SGP is located on the endosperm cells come away more cleanly and tend surface of the granules, the remainder is an to remain intact, whereas in soft wheats the subintegral part of the granule structure. Character- aleurone endosperm cells tend to fragment, a ization of the SGP by polyacrylamide gel electro- portion coming away while the rest remains phoresis in the presence of sodium dodecyl sulphate attached to the bran. has shown that the surface SGP comprized five The granularity of flour gives a measure of the polypeptides of low relative molecular mass (M,) relative hardness of the wheat, the proportion of from 5 to 30 k, while the integral SGP also the flour passing through a fine flour silk (when
CEREALS OF THE WORLD milled under standard conditions) decreasing with Protein content per se is not a factor determin increasing hardness. Greer (1949)found that the ing milling quality, except in so far as the protein percentage of the total flour passing through a no content tends to be higher in vitreous than in 16 standard silk(aperture width: 0.09 mm)under mealy wheats, and vitreousness is often associated standard conditions was 49-56% for four related with hardness and good milling quality Samples varieties of hard English wheat, whereas it was 63- of the English soft wheat varieties Riband or 71%for ten unrelated varieties of soft English wheat. Galahad may have high protein content and a The granularity of flour can also be expressed as large proportion of vitreous grains and yet mill the Particle Size Index, as determined by means of as soft wheats; on the other hand, a low-protein, an Alpine air-jet sieve. Ease of sifting, however, is predominantly mealy-grained sample of the hard affected by other factors besides hardness of varieties Hereward or mercia will mill as a hard endosperm, e.g. moisture content(cf. p. 152). wheat. The protein content of the endosperm The principal wheats of the world are arranged its quality and its chemical structure - is according to their degree of hardness as follows: however, a most important characteristicin do,, extra hard: Durum, some algerian, Indian mining baking quality(cf. p. 66) CWRS(Manitoba), American HRS Australian Prime hard Strong and weak wheats medium: Plate, Russian, some Australian American HRW, some European; Wheats yielding flour which has the ability to ft: produce bread of large loaf volume, good crumb American srw. American Soft texture, and good keeping properties(cf pp.174 White and 192) generally have a high protein content and are called'strong,, whereas those yielding Protein content four from which only a small loaf with coarse open crumb texture can be made, and which are The protein content of wheat varies over a wide characterized by low protein content, are called range(6-21%)and is influenced less by heredity weak. The flour from weak wheats is ideal for than by edaphic factors soil and climatic biscuits(cookies)and cakes, although unsuitable conditions-prevailing at the place of growth, for breadmaking unless blended with stronger nd by fertilizer treatment. Ranges of protein flour content encountered Flour from strong wheats is able to carry a wheat types are shown in Table 4.2 proportion of weak flour, i.e. the loaf maintains its large volume and good crumb structure even TABLE 4.2 when a proportion of weak four is blended with Protein Content Ranges of Wheat Types it;it is also able to absorb and retain a large Approximate q protein range The main types of wheat are classified accord ing to their baking strength HRS (United States 11,5-18 strong: CWRS (Manitoba), American HRS Russian Spring, some Australian medium: American HRW. Plate, S.E. E Russian 14.5 pean, Australian Prime Hard 8-13.5 weak: N.W. European, American SRW SRW (United States) White(United States) Hardness (milling character) and strength (baking character) are inherited separately and Sources: Schruben(1979); Kent-Jones and Amos(1947). independently(Berg, 1947). Hence, it should be
CEREALS OF THE WORLD 81 Protein content per se is not a factor determining milling quality, except in so far as the protein content tends to be higher in vitreous than in mealy wheats, and vitreousness is often associated with hardness and good milling quality. Samples of the English soft wheat varieties Riband or Galahad may have high protein content and a large proportion of vitreous grains and yet mill as soft wheats; on the other hand, a low-protein, predominantly mealy-grained sample of the hard varieties Hereward or Mercia will mill as a hard wheat. The protein content of the endosperm - its quality and its chemical structure - is, however, a most important characteristic in determining baking quality (cf. p. 66). Strong and weak wheats Wheats yielding flour which has the ability to produce bread of large loaf volume, good crumb texture, and good keeping properties (cf. pp. 174 and 192) generally have a high protein content and are called 'strong', whereas those yielding flour from which only a small loaf with coarse open crumb texture can be made, and which are characterized by OW protein content, are called 'weak'. The flour from weak wheats is ideal for biscuits (cookies) and cakes, although unsuitable for breadmaking unless blended with stronger flour. Flour from strong wheats is able to carry a proportion of weak flour, Le. the loaf maintains its large volume and good crumb structure even when a proportion of weak flour is blended with it; it is also able to absorb and retain a large Approximate quantity of water. protein range The main types of wheat are classified accordWheat ("1 type 1c16.5 strong: CWRS (Manitoba), American HRS, HRS (United States) Durum Plate (Argentina) 10-16 Russian Spring, some Australian; CWRS (Manitoba) 9-18 medium: American HRW, Plate, S.E. EuroRussian 9-14.5 Australian 8-13.5 weak: N.W. European, American SRW, English 8-13 American Soft White, Australian Soft. Other European 8-11.5 SRW (United States) 8-1 1 Hardness (milling character) and strength (baking character) are inherited separately and White (United States) 8-10.5 independently (Berg, 1947). Hence, it should be milled under standard conditions) decreasing with increasing hardness. Greer (1949) found that the percentage of the total flour passing through a No. 16 standard silk (aperture width: 0.09 mm) under standard conditions was 49-56% for four related varieties of hard English wheat, whereas it was 63- 71% for ten unrelated varieties of soft English wheat. The granularity of flour can also be expressed as the Particle Sue Index, as determined by means of an Alpine air-jet sieve. Ease of sifting, however, is affected by other factors besides hardness of endosperm, e.g. moisture content (cf. p. 152). The principal wheats of the world are arranged according to their degree of hardness as follows: extra hard: Durum, some Algerian, Indian; hard: CWRS (Manitoba), American HRS, Australian Prime Hard; medium: Plate, Russian, some Australian, American HRW, some European; soft: Some European, some Australian, American sRw7 American 'Oft White. Protein content The protein content ofwheat varies Over a wide range (621%) and is influenced less by heredity than by edaphic factors - soil and climatic conditions - prevailing at the place of growth, and by fertilizer treatment. Ranges of protein content encountered among samples of various wheat types are shown in Table 4.2. TABLE 4.2 Protein Content Ranges of Whear Types* ing to their baking strength as follows: 11.5-18 pean, Australian Prime Hard; HRW (United States) 9-14.5 * Sources: Schruben (1979); Kent-Jones and Amos (1947)
ECHNOLOGY OF CEREALS possible, through breeding, to combine good C(mainly Canadian). Proportionately more milling quality with, for example, the type of ' imported, non-EC wheat is used for breadmak gluten associated with weak wheats, to produc ng and less (possibly none) for making biscuits a good milling biscuit wheat. The varieties Slejpner, and cakes, for household flour, and for four for Haven and Maris Huntsman are hard but pos- other purposes. Thus, in 1978-1980 the average sess no particular baking strength; Minaret and composition of the grist used for breadmaking in Flanders are soft wheats which are generally the U. K. was 41% home-grown, 9% other EC acceptable for breadmaking and 50% imported, non-EC However, since 1981 there has been a consider. Grain size and shape able reduction in the quantity of imported wheat used for breadmaking(for reasons explained in The maximum yield of white flour obtainable Ch.8,p 193). Thus, in 1990/91, while the total from wheat in milling is ultimately dependent wheat milled in the U. K. comprised 87% home- upon the endosperm content, and the latter is grown, 6%other EC, and 7% imported non-EC affected by the size and shape of the grain, and the average composition of the breadmaking grist by the thickness of the bran. was approximately 79% home-grown, 10% other The specific(bushel) weight(bu wt)measure- EC, and 11% imported non-EC(see also Fig 8.1) ment(test wt per bu in the U.S.A. hectolitre wt or natural wt in Europe) estimates the weight of a fixed volume of grain, and gives a rough America indication of kernel size and shape Wheats of The principal wheat-producing countries of the high bu wt are usually considered to mill the more American continent are Canada, U.S.A. and readily and to yield more flour. However, these Argentina measurements can be misleading, as soft mealy wheats often have high bu wt. Moisture content also affects bu wt Canada Shellenberger(1961)found that the volumetr The wheat grown in western Canada is segre oran content is lower in large than in small grains, gated into five classes according to season of viz. 14. 1%and 14.6%, respectively, from samples sowing(spring or winter), grain colour(red or of the same types of wheat, showing the economic white), grain texture(hard or soft), and species importance of large kernel size (T. aestivum or T. durum). Spring-sown types predominate-over 95% of the Canadian wheat World wheats crop is spring sown-and there is more red than white, and more hard than soft. The classes U. K.-grown and imported wheats cover a further described as follows wide range in quality and characteristics. In an endeavour to produce four of regular quality the Canada Western Red Spring/CWRS British flour miller makes milling grist' by blending together various types of wheat so that CWRS wheat-formerly known as ' Manitoba particular properties lacking in one component is grown in the provinces of Manitoba, Sas- of the grist may be provided by another. katchewan and Alberta. It is a high protein wheat In recent years, the sources of imported wheat of excellent milling and baking qualities. It can used by U. K. four millers have been more be used alone, or in blends with lower-protein restricted than formerly, and comprise principally wheat, to produce hearth breads, noodles, flat the EC countries(mainly France) and Canada. breads and steam breads. CWRS wheat is marketed Of the total wheat milled in the U.K. in 1978- in three grades, of which the primary grade 1980(5 million t per an ) 56% was home-grown, characteristics are shown in Table 4.3. The mini- 7% was other EC wheat, and 37% imported, non- mum content of hard vitreous kernels is 65%for
82 TECHNOLOGY OF CEREALS possible, through breeding, to combine good EC (mainly Canadian). Proportionately more milling quality with, for example, the type of ‘imported, non-EC’ wheat is used for breadmakgluten associated with weak wheats, to produce ing and less (possibly none) for making biscuits agoodmilling biscuit wheat. Thevarieties Slejpner, and cakes, for household flour, and for flour for Haven and Maris Huntsman are hard but pos- other purposes. Thus, in 1978-1980 the average sess no particular baking strength; Minaret and composition of the grist used for breadmaking in Flanders are soft wheats which are generally the U.K. was 41% home-grown, 9% other EC, acceptable for breadmaking. and 50% imported, non-EC. However, since 1981 there has been a considerable reduction in the quantity of imported wheat used for breadmaking (for reasons explained in Grain size and shape The maximum yield of white flour obtainable Ch. 8, p. 193). Thus, in 1990/91, while the total from wheat in milling is ultimately dependent wheat milled in the U.K. comprised 87% homeupon the endosperm content, and the latter is grown, 6% other EC, and 7% imported non-EC, affected by the size and shape of the grain, and the average composition of the breadmaking grist by the thickness of the bran. was approximately 79% home-grown, 10% other The specific (bushel) weight (bu wt) measure- EC, and 11% imported non-EC (see also Fig. 8.1). ment (test wt per bu in the U.S.A.; hectolitre wt or natural wt in Europe) estimates the weight of America a fixed volume of grain, and gives a rough indication of kernel size and shape. Wheats of The principal wheat-producing countries of the high bu wt are usually considered to mill the more American continent are Canada, U.S.A. and readily and to yield more flour. However, these Argentina. measurements can be misleading, as soft mealy Canada wheats often have high bu wt. Moisture content also affects bu wt. Shellenberger (1961) found that the volumetric The wheat grown in western Canada is segrebran content is lower in large than in small grains, gated into five classes according to season of viz. 14.1% and 14.6%, respectively, from samples sowing (spring or winter), grain colour (red or of the same types of wheat, showing the economic white), grain texture (hard or soft), and species importance of large kernel size. (T. aestivum or T. durum). Spring-sown types predominate - over 95% of the Canadian wheat crop is spring sown - and there is more red than white, and more hard than soft. The classes are World wheats wide range in quality and characteristics. In an endeavour to produce flour of regular quality, the British flour miller makes a ‘milling grist’ by blending together various types of wheat so that particular properties lacking in one component of the grist may be provided by another. In recent years, the sources of imported wheat used by U.K. flour millers have been more restricted than formerly, and comprise principally the EC countries (mainly France) and Canada. Of the total wheat milled in the U.K. in 1978- 1980 (5 million t per an.), 56% was home-grown, 7% was other EC wheat, and 37% imported, nonU.K.-grown and imported wheats cover a further described as follows. Canada Western Red Spring (C WRS) CWRS wheat - formerly known as ‘Manitoba’ - is grown in the provinces of Manitoba, Saskatchewan and Alberta. It is a high protein wheat of excellent milling and baking qualities. It can be used alone, or in blends with lower-protein wheat, to produce hearth breads, noodles, flat breads and steam breads. CWRS wheat is marketed in three grades, of which the primary grade characteristics are shown in Table 4.3. The minimum content of hard, vitreous kernels is 65% for